July 10, 2013

Surface Melt Will Continue To Dominate Greenland Ice-Loss

According to research published in the Journal of Glaciology, surface ice melt will be the dominant process controlling ice-loss from Greenland.

Greenland's ice sheet is considered an important potential contributor to future global sea-level rise over the next century or longer. It contains an amount of ice that could lead to a rise of global sea-level by more than 22 feet if it completely melted. Changes in its total mass are caused by two main processes: fluctuations in melting and snowfall on its surface, and changes to the number of icebergs released from a large number of outlet glaciers into the ocean.

Ice loss from the ice sheet has increased over the last decade, with half of it attributed to changes in the surface conditions and with the remainder due to increased iceberg calving. A team from the Vrije Universiteit Brussel looked into how both processes will evolve and interact in the future. They did this using a computer model that projects the future ice sheet evolution with high accuracy using the latest available techniques and input data.

Researchers created a method to generalize projections made in earlier research that looked into just four of Greenland's outlet glaciers. They applied the earlier findings to all calving glaciers around the Greenland ice sheet. They found a total sea-level contribution from the Greenland ice sheet of two inches after 100 years for an average warming scenario and seven inches after 200 years.

"Our research has shown that the balance between the two most important mass loss processes will change considerably in the future so that changes in iceberg calving only account for a small percentage of the sea-level contribution after 200 years with the large remainder due to changes in surface conditions," said lead author Dr. Heiko Goelzer, of the Dutch-based university.

The researchers say the limited importance of outlet glacier dynamics in the future is a result of their retreat back onto land and of strong increasing surface melting due to global warming.

"This scenario is no reason to be complacent. The reason the significance of calving glaciers reduces compared to surface melting is, so much ice will be lost in coming decades that many glaciers currently sitting in fjords will retreat inland to where they are no longer affected by warming seas around Greenland," said Ice2sea coordinator Prof. David Vaughan, of the British Antarctic Survey.

The Greenland ice sheet faced a record melt during the summer of 2012, with more than 90 percent of the ice-sheet surface melting as of July 11, 2012. Scientists have published numerous papers explaining why they believe the ice sheet is melting. One team wrote in June that an unusual jet stream change could be behind the record surface melt.

NASA's Greenland Rover and Goddard Remotely Operated Vehicle for Exploration and Research (GROVER) just had its first polar experience on Greenland. This rover is built to carry ground-penetrating radar to analyze layers of snow and ice. GROVER is one of many instruments scientists are using to try and understand how our changing climate is affecting Greenland.